Biofuels comprising hydrocarbons derived from feedstock originating from renewable sources, including oils and fats originating from plants, animals, algae, fish, microbiological processes, various waste streams and sewage sludge, are used in increasing amounts as alternatives for fossil fuels or as blending stocks for fuels. The feedstock may be hydroprocessed in one or more steps to yield hydrocarbons, which further can be fractionated to liquid fuel cuts, such as diesel, gasoline, etc.
Ethanol is another widely used liquid biofuel. It is readily available by fermentation of sugar-containing feeds using yeast, however there are also alternative processes available, such as biomass gasification followed by alcohol synthesis, or gasification followed by fermentation using anaerobic bacteria.
The use of ethanol in conventional gasoline cars is usually limited to 10-15% by volume due to technical limitations of the engines. In the gasoline pool of fuels only ethanol is generally approved as blending component. 95E10, 98E5 and E85 gasoline products contain ethanol in combination with fossil fuel blending components, and further, E100 (100% ethanol) is sold in Brazil. In countries at warm climates the vapor pressure causes no problems. However, under cold climate where the temperature may be 0° C. or lower, the ethanol fuel does not meet the official fuel requirements, particularly regarding vapor pressure.
In general the conventional spark-ignited engines are not compatible with fuels having higher oxygen content. Fuels having higher ethanol blending ratios can be used in engines capable of using high ethanol fuels, such as vehicles based on Flexible Fuel Vehicle technology (FFV), and any proportion of ethanol can be used in gasoline blends. Gasoline blends containing high amounts of ethanol typically have low vapor pressure and the combustion event and idling performance may not be acceptable. Generally E85 gasoline blends shall meet the national or international standards.
Despite the ongoing research and development of liquid fuels, there is a need to provide improved biofuel compositions based on high ethanol content, useful as gasoline.